Twin screw extruder with conical non-parallel converging screws

ABSTRACT

An improved twin screw extruder device ( 14 ) is provided which is capable of producing a wide variety of high quality extrudates having greatly varying final properties, without the need for extensive machine modifications. The extruder ( 14 ) includes a barrel ( 16 ) together with a co-rotating twin screw assembly ( 22 ). The assembly ( 22 ) is made up of a pair of screws ( 50, 52 ) having central, tapered shafts ( 54, 56 ) equipped with outwardly extending helical flighting ( 58, 60 ); the screws ( 50, 52 ) are non-parallel and are positioned so that the flighting ( 58, 60 ) thereof is intercalated along the length of the screws ( 50, 52 ). The flighting is of specialized configuration and tapers along the length of the screws ( 50, 52 ) preferably at an angle of taper different than that of the shafts ( 54, 56 ); moreover, the width of the outer flighting surfaces ( 70, 72 ) increases along the length of the shafts ( 54, 56 ). This screw geometry defines a series of alternating upper and lower close-clearance high-pressure nip areas ( 78 ) defined by the flighting ( 58, 60 ) which serves to propel an extrudable mixture forwardly towards the outlet end ( 20 ) of the barrel ( 16 ). However, passageways ( 80 ) and kneading zones ( 82 ) are also defined between the screws ( 50, 52 ), which assures full mixing, shearing and cooking of the material. The extruder device ( 14 ) is capable of producing high density sinking aquatic feeds as well as expanded, low density products merely by changing the rotational speed of the screws ( 50, 52 ) together with appropriate temperature control. In another embodiment, a fluid extraction extruder ( 138 ) is provided having a specialized extruder head ( 140 ) including an outer shell ( 144 ) and an inner, elongated, slotted sleeve ( 152 ).

RELATED APPLICATION

[0001] This is a divisional of Ser. No. 10/068,181 filed Feb. 5, 2002which is a continuation-in-part of application Ser. No. 09/912,144 filedJul. 24, 2001.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention is broadly concerned with improved twinscrew extrusion devices of a highly versatile nature which can be usedfor the production of a wide variety of end products of varyingdensities, cook values and expansion ratios, without the need forextensive machine modifications. The extruders of the invention includea twin screw assembly having non-parallel, tapered conical screws withthe flighting of the screws intercalated along the length of theextruder barrel to define close-clearance, preferably constantdimension, alternating upper and lower nip areas and trailing kneadingzones and reverse flow passageways; the nip areas create high pressurezones within the barrel which propel material forwardly, while thematerial is kneaded and allowed to reverse flow in the zones andpassageways. In other embodiments, an infinitely variable die assemblyincluding a shiftable stem movable between a waste disposal position anda variety of extrusion positions. A specialized fluid extraction finalextruder head is also provided, which allows oils or other fluids to beefficiently extracted, particularly with the aid of a supercriticalextractant such as carbon dioxide.

[0004] 2. Description of the Prior Art

[0005] Extrusion cooking devices have long been used in the manufactureof a wide variety of edible and other products such as human and animalfeeds. Generally speaking, these types of extruders include an elongatedbarrel together with one or more internal, helically flighted, axiallyrotatable extrusion screws therein. The outlet of the extruder barrel isequipped with an apertured extrusion die. In use, a material to beprocessed is passed into and through the extruder barrel and issubjected to increasing levels of temperature, pressure and shear. Asthe material emerges from the extruder die, it is fully cooked andshaped and may typically be subdivided using a rotating knife assembly.Conventional extruders of this type are shown in U.S. Pat. Nos.4,763,569, 4,118,164 and 3,117,006.

[0006] Most conventional modern-day extrusion cookers are made up of aseries of interconnected tubular barrel heads or sections with theinternal flighted screw(s) also being sectionalized and mounted onpowered, rotatable shaft(s). In order to achieve the desired level ofcook, it has been thought necessary to provide relatively long barrelsand associated screws. Thus, many high-output pet food machines may havefive to eight barrel sections and have a length of from about 10 to 20times the screw diameter. As can be appreciated, such long extruders areexpensive and moreover present problems associated with properlysupporting the extrusion screw(s) within the barrel. However, priorattempts at using relatively short extruders have not met with success,and have been plagued with problems of insufficient cook and/orrelatively low yields.

[0007] U.S. Pat. Nos. 5,939,124 and 5,694,833 describe short length,high speed cooking extruders which address the problem of excessivelylong barrel and screw lengths, and thus represent a distinct advance inthe art. These extruders, sold by Wenger Manufacturing, Inc. as U P/Cextruders, have achieved considerable commercial success.

[0008] However, most prior extruders must be designed with screw andbarrel section configurations which are specific to a desired product.That is, the configuration used for the production of high densityaquatic feeds is generally significantly different than that which wouldbe necessary to produce medium density pet foods or low density feeds.As a consequence, the extruder must be broken down and reconfigured ifit is desired to change the product to be produced. Moreover, in somecases an extruder designed for one type of product simply cannot bereconfigured successfully to efficiently produce a significantlydifferent type of product.

[0009] Oils such as soybean oil are conventionally extracted fromsoybeans by mechanical extraction techniques, solvent extraction and/orsupercritical fluid technologies. For large production operations,mechanical extractors are inefficient, and the extracted oil requiresconsiderable refinement. On the other hand, supercritical fluid (e.g.,CO₂) extraction devices are too expensive and complex for existing oilplants. Solvent extraction using hexane or other solvents presentsenvironmental problems associated with disposal of the solvent.

[0010] There is accordingly a need in the art for improved extruderequipment of great flexibility and versatility and which can be used toyield dissimilar products without extensive reconfiguration or reworkingof the internal extruder components; moreover, improved equipment forthe extraction of high quality oils and the like while avoiding theproblems of solvent extraction would be an important breakthrough.

SUMMARY OF THE INVENTION

[0011] The present invention overcomes the problems outlined above andprovides a twin screw extruder having an elongated barrel with amaterial inlet and a material outlet usually equipped with a restrictedorifice die, together with specially configured extrusion screws withinthe barrel. Each screw includes an elongated central shaft having ashaft rear end and a shaft front end with outwardly extending helicalflighting provided along the length of the central shaft to provide aflighting rear end, a flighting front end and an outer flighting surfacespaced from the central shaft. The central shaft may be of constantdiameter but preferably is progressively tapered through a first taperangle along the length thereof from rear to front; similarly, theflighting may be of constant depth but is preferably tapered from rearto front through a second taper angle. Optimally but not necessarily theshaft and flighting taper angles are different, with the latter beinggreater than the former. Also, the width of the outer flighting surfacemaybe constant from rear to front but advantageously the width changesprogressively along the length of the flighting from rear to front;again most preferably, the width of the flighting increases from rear tofront so that the width of the outer flighting surface adjacent thefront end is greater than the width of the outer flighting surfaceadjacent the flighting rear end.

[0012] The twin screws are positioned in juxtaposition with the centralaxes of the shafts converging towards each other so that these axesdefine an included angle. Further, the flighting of the shafts isintercalated, preferably along the entire flighting length. In thisfashion, the screws cooperatively define a series of close-clearance,alternating upper and lower nip areas along the length of the screw set.Preferably, the flighting clearance at the respective nip areas issubstantially constant along the full length of the screw set, althoughmore generally the nip clearances may increase or decrease along thelength of the screw set. The design of the screw set to present theclose-clearance nip areas creates a series of high pressure zones withinthe extruder which serve to positively propel the material beingextruded forwardly in a “pulsing” fashion.

[0013] It has been found that the extruder design affords a high degreeof operational flexibility, so that the extruder may be used to producea variety of products simply by changing the rotational speed of thescrew assembly and possibly other processing condition changes (e.g.,temperature and die configuration). It has been observed that changes inpreconditioning perimeters have a more pronounced effect on the endproduct, than is common with conventional extrusion equipment.Accordingly, the simple expedient of changing steam and/or water inputto the preconditioner can in and of itself significantly impact theproperties of the final extrudate.

[0014] In another aspect of the invention, an extruder design forextraction of fluids such as oil from oil seed materials is provided.Such an extruder preferably although not necessarily includes thefeatures described above, but includes an extruder head sectionincluding an outer shell equipped with a fluid outlet, together with aninternal, elongated, slotted sleeve which receives a portion of theextruder screw(s). The sleeve is preferably constructed from a series ofelongated bar members which are welded or otherwise affixed together toform a tubular sleeve, with passageways between adjacent bars. Thepassageways are preferably tapered and present a smaller opening at theinterior of the sleeve, as compared with the exterior thereof. In use,an oil seed or other material is passed through the extruder so that inthe head section the fluid to be recovered is pressed or extrudedthrough the sleeve passageways. Fluid extraction is materially enhancedby injection of a supercritical fluid such as carbon dioxide or propaneinto the extruder head section.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a partially schematic side elevational view of anextrusion system including the improved extruder device in accordancewith the invention;

[0016]FIG. 2 is a perspective view of the preferred twin extrusion screwset used in the extruder device;

[0017]FIG. 3 is a fragmentary horizontal sectional view of the preferredtwin screw extruder;

[0018]FIG. 4 is a vertical sectional view of the twin screw extruder;

[0019]FIG. 5 is a fragmentary, greatly enlarged top view of portions ofthe twin screw assembly, illustrating in detail the intercalation of thescrew flighting and the close-clearance nip zones between the flighting;

[0020]FIG. 6 is a horizontal sectional view of the twin screw portionsillustrated in FIG. 5;

[0021]FIG. 7 is a fragmentary vertical sectional view illustrating anextruder in accordance with the invention equipped with a variableoutput die assembly, the latter in a full-open condition;

[0022]FIG. 8 is a fragmentary sectional view taken along line 8-8 ofFIG. 7;

[0023]FIG. 9 is a fragmentary vertical sectional view similar to that ofFIG. 7 but depicting the die assembly in the diverter condition thereof;

[0024]FIG. 10 is a sectional view taken along line 10-10 of FIG. 7;

[0025]FIG. 11 is a fragmentary vertical sectional view of an extruder inaccordance with the invention, equipped with a final head designed forextraction of oil from oil seeds;

[0026]FIG. 12 is a vertical sectional view taken along line 12-12 ofFIG. 11;

[0027]FIG. 13 is a perspective view of one of the bar elements used inthe fabrication of the final head illustrated in FIGS. 11 and 12; and

[0028]FIG. 14 is a perspective view of a pair of adjacent bar elements,depicting an oil extraction slot between the bar elements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0029] Embodiment of FIGS. 1-6

[0030] Turning now to the drawings, FIG. 1 illustrates an extrusionsystem 10 made up of a preconditioner 12 as well as a twin screwextruder device 14. The device 14 broadly includes a sectionalizedbarrel 16 presenting an inlet 18 and an outlet 20, with a specializedtwin screw assembly 22 within the barrel 16; the assembly 22 is coupledvia a gear box drive 24 to motor 26.

[0031] The preconditioner 12 is designed to initially moisturize andpartially precook dry ingredients prior to passage thereof as a dough orthe like into the inlet 18 of device 14. To this end, the preconditioner12 is typically in the form of an elongated chamber equipped withrotatable internal paddles as well as injection ports for water and/orsteam. A variety of preconditioners maybe used in the context of theinvention. However, it is particularly preferred to use Wenger DDCpreconditioners of the type described in U.S. Pat. No. 4,752,139,incorporated by reference herein.

[0032] The barrel 16 in the embodiment illustrated is made up of threeend-to-end interconnected tubular barrel heads 28, 30, 32, each providedwith an external jacket 34, 36, 38 to allow circulation of cooling orheating media for temperature control of the extruder device. It will beobserved that the first head 28 includes the inlet 18, whereas the lasthead 32 is designed to accept a die assembly 40. Each of the heads 28-32also includes an internal sleeve 42, 44 and 46 which cooperativelydefine a tapered, continuous screw assembly-receiving opening 48 withinthe barrel. This opening 48 has a generally “figure eight” shape inorder to accommodate the screw assembly 22. As illustrated, the opening48 is widest at the rear end of head 28 and progressively and uniformlytapers to the end of head 32.

[0033] The screw assembly 22 includes first and second elongated screws50, 52 which are in side-by-side relationship as best seen in FIGS. 2and 3. Each of the screws 50, 52 includes an elongated central shaft 54,56 as well as outwardly extending helical flighting 58, 60. The shafts54, 56 each have an outer surface which is progressively and uniformlytapered through a first taper angle from points 62, 64 proximal to therear ends of the corresponding shafts 54, 56, to forward points 66, 68adjacent the forward ends of the shafts. This taper angle varies fromabout 0.5-5°, and more preferably from about 1-2.2°. The presentembodiment has a taper angle of 1.3424°.

[0034] The flighting 58, 60 (in the embodiment illustrated doubleflights are used, but single or multiple flights are also a possibility)extends essentially the full length of the shafts 52, 54 between points62, 66 and 64, 68. Thus, the flighting 58, 60 proceeds from a rear endadjacent the point 62, 64 in a continuous fashion to the forward point66, 68. In addition, the flighting presents an outer surface 70, 72 oneach of the screws 50, 52, having a width denoted by “W” in FIG. 6, aswell as a flight depth between the outer surface of the central shaftand the outer flighting surface, denoted by “D” in FIG. 6. The geometryof the flighting 58, 60 is such that the flight depth D progressivelyand uniformly decreases as the flighting proceeds from the rear end tothe front end of the screws 50, 52. Consequently, the outer surfaces 70,72 of the flighting 58, 60 also taper from rear to front in aprogressive and uniform fashion. The second angle of taper of theflighting depth and the outer flighting surfaces ranges from 2-6° andmore preferably from about 2.5-4°. The precise second angle of taper inthe illustrated embodiment is 3.304°.

[0035] Finally, the flighting 58, 60 is designed so that the width “W”of the flighting outer surfaces 70, 72 increases in a progressive anduniform fashion from the rear end of the screws to the front endsthereof. This configuration is best illustrated in FIGS. 3 and 4, whereit will be seen that the width W is relatively small at the rear ends ofthe screws 50, 52, but increases to a wider width W at the forward endsof the screws. As indicated previously however, the width W may beconstant throughout the length of the screws, or could narrow from therearward ends to the forward ends thereof. Accordingly, the ratio of thewidth at the forward or input end of each screw to the width at therearward or output end ranges from about 0.5 to 5, and more preferablyfrom about 1 to 3.

[0036] The screws 50, 52 are oriented so that their respective centeraxes 74, 76 (see FIG. 5) are at a converging angle relative to eachother, so that an included angle is defined by the center axes. Thisincluded angle generally ranges from about 1-8°, more preferably fromabout 1.5-5°. The included angle in the illustrated embodiment is2.3240°. When the screws 50, 52 are oriented as described within barrelopening 48, the flighting 58, 60 of the respective screws 50, 52 isintercalated, i.e., each of the flightings defines an imaginary frustumof a cone between the rear and front ends of the corresponding screws,and the flighting 58, 60 extends within the imaginary frustum of theadjacent screw.

[0037] Attention is next directed to FIGS. 5 and 6 which depicts indetail the intercalation of the flighting 58, 60. As shown, and byvirtue of the selection of appropriate first and second taper angles andthe included angle between the center axes 74, 76, the flightingpresents a plurality of close-clearance nip zones 78 along the length ofthe screw assembly 22. These nip areas present a clearance between theflightings 58, 60 which is preferably substantially constant along thelength of the screw assembly 22. More generally, if desired such nipclearances could increase or decrease along the length of the assembly22. In practice, the clearance at the nip zones ranges from about0.010-0.2 inches, and more preferably from about 0.025-0.1 inches. Theparticular illustrated embodiment exhibits an as-manufactured clearanceat the nip areas of 0.039 inch. In addition to the nip areas 78, it willbe observed that the assembly 22 also presents material backflowpassageways 80 and kneading zones 82 between the screws 50, 52. Thesefeatures are important for purposes to be described.

[0038] The gear box drive 24 is a device especially designed toaccommodate non-parallel shafts and broadly includes an adapter housing84 together with a pair of couplers 86 for connection to the splinedends of the shafts 54, 56. The drive motor 26 is itself entirelyconventional, and is sized to drive the extruder device 14 atappropriate rotational speeds under the loads encountered.

[0039] In the operation of system 10, a variety of end products can beproduced having a multitude of final properties such as percentexpansion, density, percentage cook and other parameters. Broadlyspeaking, it is preferred that the extrudable mixtures fed into andthrough the system 10 include respective quantities of protein-bearingand starch-bearing materials and also usually a quantity of fat andadded moisture. Typical grain ingredients used in the extrudablemixtures are selected from the group consisting of wheat, corn, oats,barley, rye, sorghum, soybean, rice and mixtures thereof, while starchescan be used from any grain, root or tuber starch source. Also,additional ingredients such as surfactants and inert fillers can form apart of the extrudable mixtures. Most useful extrudable feed mixturescontain from about 30-75% by weight total protein, more preferably fromabout 40-65% by weight total protein; total starch content of from 0-25%by weight, more preferably from about 5-20% by weight; and a fat contentof from about 4-12% by weight, more preferably from about 6-10% byweight.

[0040] In the first step of a typical extrusion run, the extrudablemixture is dry blended and fed into preconditioner 18. Duringpreconditioning, the mixture is further blended and steam and/or waterare added so as to at least partially precook the mixture. Whileconditions within the preconditioner are variable, as a general practicethe mixture should be heated to a temperature of from about 125-210° F.,more preferably from about 175-210° F., in the preconditioner. Theaverage residence time in the preconditioner ranges from about 15-600seconds, more preferably from about 120-300 seconds.

[0041] After preconditioning, the extrudable mixture is passed into andthrough the extruder device 14. The screw assembly 22 is rotated so asto co-rotate the screws 50, 52, usually at a speed of from about200-1,200 rpm and more preferably from about 400-750 rpm. Pressureswithin the extruder are usually at a maximum just adjacent the outletdie, and usually range from about 500-21,000 kPa, more preferably fromabout 1,000-10,500 kPa. Maximum temperatures within the extrudernormally range from about 150-550° F., more preferably from about160-300° F. Average residence time of the mixture within the extruderdevice is from about 2-25 seconds, more preferably from about 4-15seconds, and most preferably from about 6-10 seconds.

[0042] Extrusion conditions are created within the device 14 so that theproduct emerging from the extruder barrel usually has a moisture contentof from about 8-35% by weight wet basis, more preferably from about15-22% by weight wet basis. The moisture content is derived from nativewater of the ingredients, moisture added during preconditioning and/orany water injected into the extruder barrel during processing. In termsof expansion, the level of expansion can be from 0-75%, i.e., thediameter of the extrudate may have essentially the same diameter as thedie openings (which would be 0% expansion), or may be enlarged to have adiameter of 1.75 times the diameter of the die openings (representing75% expansion). The products as extruded usually exhibit from about70-90% starch gelatinization, which is a measure of the degree of cookof the product; however, it is believed that the protein content is notcompletely denatured in many of the products, but this is dependent uponthe particulars of the extrudable mixture and the extrusion conditions.Bulk densities of the products normally range from about 24-700 g/L,more usually from about 290-500 g/L. The products can also have a widerange of pellet durability index (PDI) values usually on the order offrom about 65-99, more preferably from about 80-97.

[0043] During passage of the extrudable mixture through the barrel 16,the screw assembly 22 acts on the mixture to create, together with theendmost die 40, the desired product. The specific configuration of thescrews 52, 54 as described above generates conditions not heretoforefound with conventional twin screw extruders. That is, as the mixture isadvanced along the length of the co-rotating screws 52, 54, itcontinually encounters the alternately upper and lower close-clearancenip areas 78 which generate relatively high localized pressures servingto push or “pump” the material forwardly; at the same time, the productis kneaded within the zones 82 as the screws rotate, and backflow ofmaterial is allowed through the passageways 80. The result is an intensemixing/shearing and cooking action within the barrel 16. Furthermore, ithas been found that a wide variety of products may be produced using theequipment of the invention; simply by changing the rotational speed ofthe screw assembly 22 and, as necessary, temperature conditions withinthe barrel. For example, relatively dense sinking aquatic feeds may beproduced in good yield with the machine configuration illustratedherein; however, light density bird feeds can also be made on the verysame equipment, merely by changing the operational characteristics ofthe machine. This degree of flexibility and versatility is unprecedentedin the extrusion art.

[0044] The following examples set forth a series of extrusion runs forthe production of several types of feeds, using the improved twin screwextruder device of the invention. It is to be understood, however, thatthese examples are provided by way of illustration and nothing thereinshould be taken as a limitation upon the overall scope of the invention.

EXAMPLE 1

[0045] In this example, an extruder in combination with a preconditionerwas employed in the manufacture of high quality salmon feed atcommercial production rates.

[0046] The extruder was of the type depicted in FIG. 1, and consisted ofthree heads. In particular, the extruder configuration used in Runs #1-7was made up of the following components (where all parts are identifiedwith Wenger Mfg. Co. part numbers): extruder model C²TX; extruderbarrel-74002-424 (head No. 1); two 74002-425 (heads Nos. 2 and 3); HeadNo. 1 was equipped with sleeve 74002-421; Head No. 2 was equipped withsleeve 74002-422; Head No. 3 was equipped with sleeve 74002-423. Finaldie—65534-003 NA; 53672-003 AD; 31950-397 IN; and 65422-015 NA. Arotating knife assembly was positioned adjacent the outlet of the diefor cutting the extrudate into a convenient size. The knife assemblyincluded the following: 19462-015 (knife holder) and twelve knife blades(19430-007).

[0047] The preconditioner used in these runs was a Wenger Model 54 DDCpreconditioner in the 377 configuration with the left and right shaftsbeing equipped with 60 beaters each.

[0048] The aquatic feed recipes used in each run are set forth inTable 1. TABLE 1 Run Run Run Run Run Run Run Ingredient #1 #2 #3 #4 #5#6 #7 Fish Meal % wt 72.00 78.00 84.00 90.32 98.00 79.80 68.04 WheatFlour % wt 13.00 10.00  7.00 — — — — (from Wenger) Wheat Flour % wt13.00 10.00  7.00  7.53 —  6.66 — (from Lasi) Dicalcium Phosphate % wt 1.00  1.00  1.00  1.08  1.00  0.94  1.63 Calcium Carbonate % wt  1.00 1.00  1.00  1.08  1.00  0.94  1.63 Soybean Meal — — — — —  6.66 — SoyConcentrate (from % wt — — — — —  5.00 28.70 Central Soya)

[0049] The following table sets forth the operating conditions for thepreconditioner and extruder devices in the seven runs. TABLE 2 RUN #1RUN #2 RUN #3 RUN #4 RUN #5 RUN #6 RUN #7 DRY RECIPE INFORMATION: DryRecipe Moisture % wb 10.31 9.28 9.37 9.71 8.86 7.96 7.81 Feed ScrewSpeed rpm 40 33 33 33 33 33 33 Dry Feed Rate kg/hr 4800 4000 4000 40004000 4000 4000 PRECONDITIONING INFORMATION: Preconditioner Speed rpm 250— — 250 250 250 250 Steam Flow to Preconditioner kg/hr 236 262 290 286262 262 262 Water Flow to Preconditioner kg/hr 216 239 239 239 239 239239 Preconditioner Discharge Temp. ° F. 184 194 206 206 206 196 197Moisture Entering Extruder % wb 18.2 — 19.4 19.3 20.3 20.3 19.8Estimated Retention Time in Preconditioner** min 4.8 5.8 5.8 5.8 5.8 5.85.8 EXTRUSION INFORMATION: Extruder Shaft Speed rpm 601 676 676 676 676670 670 Motor Load % 92 96 89 81 71 88 91 Power Usage kwh/ton 43 54 5046 40 50 51 Water Flow to Extruder kg/hr 21 21 21 21 21 21 21Control/Temperature-2nd Head ° F. Off/235 Off/268 Off/295 Off/310Off/320 Off/215 Off/264 Control/Temperature-3rd Head ° F. Off/195 237265 277 294 175 212 Head/Pressure kPa 10340 9310 8270 6900 5170 62106900 FINAL PRODUCT INFORMATION: Wet Bulk Density g/l 447 447 448 480 460490 455 Extruder Discharge Moisture % wb 1.5 — 17.5 18.5 18.5 18.8 16.8

[0050] The extrudate product was analyzed and rated for industrialacceptability. The results are shown in Table 3. As used in Table 3, PDIrefers to “pellet durability index.” PDI is an art recognized durabilitytest described in Feed Manufacturing Technology IV, American FeedAssociation, Inc., 1994, pages 121-122 (and referenced information),incorporated by reference herein. In such a durability test, thedurability of pellets obtained immediately after cooling when thepellets have a temperature within 110° F. of ambient temperature.Durability is determined by tumbling a 500 g sample of pre-sievedpellets (to remove fines) for 5 minutes at 50 rpm in a dust-tight12″×12″×5″ enclosure equipped with a 2″×9″ internal plate affixedsymmetrically along a 9″ side to a diagonal of one 12″×12″ of theenclosure. The enclosure is rotated about an axis perpendicular to andcentered on the 12″ sides thereof. After tumbling, the fines are removedby screening, and the pellet sample is reweighed. Pellet durability isdefined as:

durability=weight of pellets after tumbling/weight of pellets beforetumbling×100

[0051] Industrial acceptability was based upon four industry objectives:(1) PDI of 95 or greater; (2) fat and protein levels each above 35%after coating; (3) extrude at the lowest possible moisture levels todecrease drying costs, typically 18-20%; and (4) maximum ingredientflexibility by reducing starch levels to 5-10%. TABLE 3 % Bulk Wheat %Soy Density Acceptable Sample % Starch % Fat % Protein Flour Protein PDI(g/l) to Industry Run #1 18.2 7.4 46.6 26 0 96.5 484 yes Run #2 14.0 7.949.8 20 0 95.9 420 yes Run #3 9.8 8.4 52.8 14 0 95.0 434 yes Run #4 4.99.0 55.8 7 0 95.0 491 yes Run #5 0 9.6 59.6 0 0 82.0 444 no Run #6 4.97.9 56.1 7 11.6 91.6 475 no Run #7 0 6.7 61.4 0 28.7 83.0 437 no Run #80 6.7 61.4 0 28.7 — 560 no

[0052] The extrudate product was then vacuum spray coated with fish oiland analyzed. The results are shown in Table 4. TABLE 4 % Bulk Max.Vacuum Wheat Density Fat Absorption Acceptable Sample % Starch % Fat %Protein Flour (g/l) (%) to Industry Run #1 13.1 33.1 33.6 18.8 671 38.5yes Run #2 9.2 39.4 32.8 13.2 638 51.9 yes Run #3 6.6 38.3 35.6 9.4 64448.4 yes Run #4 3.6 32.7 41.2 5.2 664 35.3 yes Run #5 0 34.3 43.3 0 61037.5 no Run #6 3.6 32.3 41.3 5.2 645 35.8 no Run #7 0 32.8 44.2 0 60638.8 no Run #8 0 20.6 52.2 0 658 17.5 no

EXAMPLE 2

[0053] In this example, an extruder coupled with a preconditioner of thetype shown in FIG. 1 was used to manufacture a high quality, dry dogfood.

[0054] Specifically, the three-head extruder configuration used in Run 8was made up of the following components (where all parts are identifiedwith Wenger Mfg. Co. part numbers): extruder model C²TX; extruderbarrel-74002-424 (head No. 1); two 74002-425 (heads Nos. 2 and 3); HeadNo. 1 was equipped with sleeve 74002-421; Head No. 2 was equipped withsleeve 74002-422; Head No. 3 was equipped with sleeve 74002-423. Finaldie—65534-003 NA; 53672-003 AD; 31950-397 IN; 65421-003 BH; and31350-779 IN. A rotating knife assembly was positioned adjacent theoutlet of the die for cutting the extrudate into a convenient size. Theknife assembly included the following: 19462-015 (knife blade holder)and twelve knife blades (19430-007).

[0055] In the case of Run 9, the extruder configuration was made up ofthe following components: extruder model C²TX; extruder barrel-74002-424(head No. 1); two 74002-425 (heads Nos. 2 and 3); Head No. 1 wasequipped with sleeve 74002-421; Head No. 2 was equipped with sleeve74002-422; Head No. 3 was equipped with sleeve 74002-423. Finaldie—65534-003 NA; 53672-003 AD; 31950-400 IN; 65421-003 BH; and31350-779 IN. A rotating knife assembly was positioned adjacent theoutlet of the die for cutting the extrudate into a convenient size. Theknife assembly included the following: 19462-015 (knife blade holder)and twelve knife blades (19430-007).

[0056] In the case of Run 10, the extruder configuration was made up ofthe following components: extruder model C²TX; extruder barrel-74002-424(head No. 1); two 74002-425 (heads Nos. 2 and 3); Head No. 1 wasequipped with sleeve 74002-421; Head No. 2 was equipped with sleeve74002-422; Head No. 3 was equipped with sleeve 74002-423. Finaldie—65534-003 NA; 53672-003 AD; 31950-399 IN; 65421-003 BH; and31350-779 IN. A rotating knife assembly was positioned adjacent theoutlet of the die for cutting the extrudate into a convenient size. Theknife assembly included the following: 19462-015 (knife blade holder)and twelve knife blades (19430-007).

[0057] In the case of Run 11, the extruder configuration was made up ofthe following components: extruder model C²TX; extruder barrel-74002-424(head No. 1); two 74002-425 (heads Nos. 2 and 3); Head No. 1 wasequipped with sleeve 74002-421; Head No. 2 was equipped with sleeve74002-422; Head No. 3 was equipped with sleeve 74002-423. Finaldie—65534-009 AD; 65134-003 BD; 53672-003 AD; 31950-399 IN; 65421-003BH; and 31350-779 IN. A rotating knife assembly was positioned adjacentthe outlet of the die for cutting the extrudate into a convenient size.The knife assembly included the following: 19462-015 (knife bladeholder) and twelve knife blades (19430-007).

[0058] The preconditioner used in all four of these setups was a WengerModel 54 DDC preconditioner having Configuration No. 377. The left andright shafts were each equipped with a total of sixty beaters.

[0059] In Runs 8-11 inclusive, the starting recipe was made up of 38.00%by weight corn, 18.00% by weight wheat midlings, 16.00% by weightsoybean meal, 8.00% by weight corn gluten, and 20.00% by weight meat andbone meal.

[0060] The following table sets forth the operating conditions for thepreconditioner and extruder devices in the four runs. TABLE 5 RUN RUNRUN RUN #8 #9 #10 #11 DRY RECIPE INFORMATION: Feed Screw Seed rpm 36 5040 45 PRECONDITIONING INFORMATION: Steam Flow to Preconditioner kg/hr155 186 160 1303 Water Flow to Preconditioner lb/hr 770 440 510 1000Preconditioner Discharge Temp. ° F. 191 198 193 205 Moisture EnteringExtruder % wb 23.04 20.2 — 23.32 EXTRUSION INFORMATION: Extruder ShaftSpeed rpm 600 600 600 600 Motor Load % 93 86 42 91Control/Temperature-2nd Head ° F. 219 226 245 — Control/Temperature-3rdHead ° F. 200 218 270 — Head/Pressure kPa 1500 1200 1100 800 FINALPRODUCT INFORMATION: Extruder Discharge Moisture % wb 22.06 23.05 23.4423.97 Extruder Discharge Rate kg/hr 6545 7527 7527 7000 ExtruderDischarge Density kg/m³ 224 340 384 400 Extruder Performance StableStable Stable Stable Final Product Description Dog Dog Dog Dog Food FoodFood Food Run Rating Good Good Good —

EXAMPLE 3

[0061] In this example, an extruder in combination with a preconditionerwas employed in the manufacture of high quality aquatic feed atcommercial production rates.

[0062] The extruder was of the type depicted in FIG. 1, and consisted ofthree heads. In particular, the extruder configuration used in Run 12was made up of the following components (where all parts are identifiedwith Wenger Mfg. Co. part numbers): extruder model C²TX; extruderbarrel-74002-424 (head No. 1); two 74002-425 (heads Nos. 2 and 3); HeadNo. 1 was equipped with sleeve 74002-421; Head No. 2 was equipped withsleeve 74002-422; Head No. 3 was equipped with sleeve 74002-423. Finaldie—65534-003 NA; 53672-003 AD; 31950-397 IN; and 65422-015 NA. Arotating knife assembly was positioned adjacent the outlet of the diefor cutting the extrudate into a convenient size. The knife assemblyincluded the following: 19462-015 (knife blade holder) and twelve knifeblades (19430-007).

[0063] The preconditioner used in these runs was a Wenger Model 54 DDCpreconditioner having configuration 377 with the right and left shaftscontaining 60 beaters each.

[0064] The recipe used in Run #12 was 72.00% by weight fish meal, 26.00%by weight wheat flour, 1.00% by weight calcium phosphate, and 1.00% byweight calcium carbonate.

[0065] The following table sets forth the operating conditions for thepreconditioner and extruder devices in the run. TABLE 6 RUN #12 DRYRECIPE INFORMATION: Feed Screw Speed rpm  54 PRECONDITIONINGINFORMATION: Steam Flow to Preconditioner kg/hr 405 Water Flow toPreconditioner lb/hr 325 Preconditioner Discharge Temp. ° F. 202EXTRUSION INFORMATION: Extruder Shaft Speed rpm 609 Motor Load %  80Head/Pressure kPa 1100  FINAL PRODUCT INFORMATION: Extruder DischargeRate kg/hr 6200  Final Product Description Fish Food

EXAMPLE 4

[0066] In this example, an extruder was employed in the manufacture ofhigh quality corn based snack food at commercial production rates.

[0067] The extruder was of the type depicted in FIG. 1, and consisted ofthree heads. In particular, the extruder configuration used in Runs 13and 14 was made up of the following components (where all parts areidentified with Wenger Mfg. Co. part numbers): extruder model C²TX;extruder barrel-74002-424 (head No. 1); two 74002-425 (heads Nos. 2 and3); Head No. 1 was equipped with sleeve 74002-421; Head No. 2 wasequipped with sleeve 74002-422; Head No. 3 was equipped with sleeve74002-423. Final die—65534-029 AD; 31950-399 IN; and 74010-959 BD. Arotating knife assembly was positioned adjacent the outlet of the diefor cutting the extrudate into a convenient size. The knife assemblyincluded the following: 19462-023 (knife blade holder) and five knifeblades (19430-007).

[0068] The recipe used in Runs #13 and #14 was 100.00% by weight snackmeal.

[0069] The following table sets forth the operating conditions for theextruder device in the run. TABLE 7 RUN #13 RUN #14 DRY RECIPEINFORMATION: Feed Screw Speed rpm 999 999 EXTRUSION INFORMATION:Extruder Shaft Speed rpm 599 599 Motor Load %  43  44 Head/Pressure kPa3/5516 3/5860.8 FINAL PRODUCT INFORMATION: Extruder Discharge Rate kg/hr460 — Extruder Discharge Density kg/m³  46  33 Run Rating Good GoodExtruder Performance Stable Stable Final Product Description Corn CornCurls/ Curls Balls

EXAMPLE 5

[0070] In this example, an extruder was employed in the manufacture ofhigh quality cooked grains (corn) at commercial production rates.

[0071] The extruder was of the type depicted in FIG. 1, and consisted ofthree heads. In particular, the extruder configuration used in Runs14-18 was made up of the following components (where all parts areidentified with Wenger Mfg. Co. part numbers): extruder model C²TX;extruder barrel-74002-424 (head No. 1); two 74002-425 (heads Nos. 2 and3); Head No. 1 was equipped with sleeve 74002-421; Head No. 2 wasequipped with sleeve 74002-422; Head No. 3 was equipped with sleeve74002-423. Runs 15 and 16 employed a final die—74002-527 NA; 31950-399IN; 65421-001 BH; and 31350-895 IN. Runs 17 and 18 employed a finaldie—74002-527 NA; 31950-356 IN; 65421-001 BH; and 31350-895 IN. Arotating knife assembly was positioned adjacent the outlet of the diefor cutting the extrudate into a convenient size. The knife assemblyincluded the following: 19462-015 (knife blade holder) and twelve knifeblades (19430-007).

[0072] The preconditioner used in these runs was a Wenger Model 54 DDCpreconditioner having configuration 377 with the right and left shaftscontaining 60 beaters each.

[0073] The grain used in Runs #15-#18 was corn.

[0074] The following table sets forth the operating conditions for theextruder device in the run. TABLE 8 RUN RUN RUN RUN #15 #16 #17 #18 DRYRECIPE INFORMATION: Feed Screw Seed rpm 20 11 21 21 PRECONDITTONERINFORMATION: Preconditioner Speed rpm 250 250 250 250 Steam Flow toPreconditioner kg/hr 407 129 530 603 Water Flow to Preconditioner lb/hr152 56 500 100 Preconditioner Discharge Temperature ° F. 156 147 147 160EXTRUSION INFORMATION: Extruder Shaft Speed rpm 600 604 600 613 MotorLoad % 107 92 70 94 Water Flow to Extruder lb/hr 100 — 160 100Control/Temperature 2nd Head ° F. 268 177 155 W/164 Control/Temperature3rd Head ° F. 212 206 183 W/171 Head/Pressure kPa 13790 13790 689511721.5 FINAL PRODUCT INFORMATION: Extruder Discharge Rate kg/hr 3338.44— — 3265.86 Extruder Discharge Density kg/m³ 390 144 593 481 FinalProduct Description Corn Corn Corn Corn

EXAMPLE 6

[0075] In this example, an extruder was employed in the manufacture ofhigh quality cooked grains (general/mixed) at commercial productionrates.

[0076] The extruder was of the type depicted in FIG. 1, and consisted ofthree heads. In particular, the extruder configuration used in Runs 19and 20 was made up of the following components (where all parts areidentified with Wenger Mfg. Co. part numbers): extruder model C²TX;extruder barrel-74002-424 (head No. 1); two 74002-425 (heads Nos. 2 and3); Head No. 1 was equipped with sleeve 74002-421; Head No. 2 wasequipped with sleeve 74002-422; Head No. 3 was equipped with sleeve74002-423. Final die—74002-527 NA; 31950-356 IN; 65421-001 BH; and31350-895 IN. A rotating knife assembly was positioned adjacent theoutlet of the die for cutting the extrudate into a convenient size. Theknife assembly included the following: 19462-015 (knife blade holder)and twelve knife blades (19430-007).

[0077] The preconditioner used in these runs was a Wenger Model 54 DDCpreconditioner having configuration 377 with the right and left shaftscontaining 60 beaters each. The extruded product was then dried.

[0078] The following table sets forth the operating conditions for theextruder device in the run. TABLE 9 Run #19 Run #20 DRY RECIPEINFORMATION: Feed Screw Speed rpm  21  12 PRECONDITIONER INFORMATION:Preconditioner Speed rpm 250 250 Steam Flow to Preconditioner kg/hr 550766 Water Flow to Preconditioner lb/hr 300 — Preconditioner DischargeTemperature ° F. 170 192 EXTRUSION INFORMATION: Extruder Shaft Speed rpm613 613 Motor Load % 105  80 Water Flow to Extruder lb/hr 100  25Control/Temperature 2nd Head ° F. W/178 W/175 Control/Temperature 3rdHead ° F. W/182 Head/Pressure kPa 11721.5 11721.5 DRYER INFORMATION:Zone 1 Temperature ° C. 110 110 Zone 2 Temperature ° C. 110 110Retention Time—Pass 1 min 9 9 Retention Time—Pass 2 min 11 11 Fan Speed1 rpm 1800 1800 Fan Speed 2 rpm 1800 1800 Fan Speed 3 rpm 1800 1800 FanSpeed 4 rpm 1800 1800 FINAL PRODUCT INFORMATION: Extruder Discharge Ratekg/hr 453.59 406 Extruder Discharge Density kg/m³ 593 150 Final ProductDescription Rice Rice

EXAMPLE 7

[0079] In this example, an extruder was employed in the manufacture ofhigh quality bird feed at commercial production rates.

[0080] The extruder was of the type depicted in FIG. 1, and consisted ofthree heads. In particular runs #21-28 used the following commoncomponents (where all parts are identified with Wenger Mfg. Co. partnumbers): extruder model C²TX; extruder barrel-74002-424 (head No. 1);two 74002-425 (heads Nos. 2 and 3); Head No. 1 was equipped with sleeve74002-421; Head No. 2 was equipped with sleeve 74002-422; Head No. 3 wasequipped with sleeve 74002-423. The runs employed final die assembliesas noted in the table below (all parts identified with Wenger Mfg. Co.part numbers): TABLE 10 Runs #21-#22 Run #23 Runs #24-#25 Run #26 Run#27-#28 Final 74002-527 NA 74002-527 NA 74002-527 NA 74002-527 NA74002-527 NA die 31950-356 IN 65534-029 AD 65534-029 AD 31950-597 IN31950-597 IN 65422-097 BD 65421-001 BH 31950-399 IN 65421-001 BH65422-001 BD 74010-587 NA 65421-001 BH 65534-029 AD 31950-356 IN

[0081] A rotating knife assembly was positioned adjacent the outlet ofthe die for cutting the extrudate into a convenient size. The knifeassembly included the following: 19462-015 (knife blade holder) andtwelve knife blades (19430-007).

[0082] The preconditioner used in these runs was a Wenger Model 54 DDCpreconditioner having configuration 377 with the right and left shaftscontaining 60 beaters each. The extruded product was then dried.

[0083] The following table sets forth the operating conditions for theextruder device in the run. TABLE 11 Run Run Run Run Run Run Run Run #21#22 #23 #24 #25 #26 #27 #28 DRY RECIPE INFORMATION: Feed Screw Seed rpm15 10 11 10 10 10 10 10 PRECONDITIONING INFORMATION: PreconditionerSpeed rpm 250 250 250 250 250 250 250 — Steam Flow to Preconditionerkg/hr 158 870 913 600 600 600 173 142 Water Flow to Preconditioner lb/hr350 — 450 — 340 200 — — Preconditioner Additive 1 Rate kg/hr — — — — 582100 — — Preconditioner Discharge Temp. ° F. 158 — — 189 189 191 — 169EXTRUSION INFORMATION: Extruder Shaft Speed rpm 600 600 610 600 600 625581 593 Motor Load % 43 37 24 62 40 47 70 95 WaterFlowtoExtruder lb/hr100 — 100 — 100 100 80 50 Control/Temperature-2nd Head ° F. W/119 WW/154 W/254 W/273 W/262 W/292 — Control/Temperature-3rd Head ° F. W/145W/174 W/138 W/174 W/172 W/168 W/182 — Head/Pressure kPa 3447.5 5516 275811032 6205.5 7584.5 13790 13790 DRYER INFORMATION: Zone 1 Temperature °C. 110 110 130 125 125 125 105 90 Zone 2 Temperature ° C. 110 110 130125 125 125 105 90 Retention Time-Pass 1 min 6 6 7.1 7.1 7.1 7.1 7.1 7.1Retention Time-Pass 2 min 9.1 9.1 9.1 9.1 9.1 9.1 9.1 9.1 DryerDischarge Moisture % wb 8.94 3.59 8.71 2.75 3.34 2.94 1.72 4.18 FanSpeed 1 rpm 2110 2110 2110 2110 2110 2110 2110 1825 Fan Speed 2 rpm 21102110 2110 2110 2110 2110 2110 1815 Fan Speed 3 rpm 2060 2060 2060 20602060 2060 2060 1800 Fan Speed 4 rpm 2095 2095 2095 2060 2060 2060 20951800 FINAL PRODUCT INFORMATION: Extruder Discharge Rate kg/hr 3469 — —1818 1818 — 1658 — Extruder Performance — — — — — — — Unstable ExtruderDischarge Density kg/m³ 561 497 570 260 352 390 230 216.35 Final ProductDescription KT Test KT Test KT Test KT Test KT Test KT Test KT KT TestTest- .062

EXAMPLE 8

[0084] In this example, an extruder was employed in the manufacture ofhigh quality dog food at commercial production rates.

[0085] The extruder was of the type depicted in FIG. 1, and consisted ofthree heads. In particular, the extruder configuration used in Runs29-31 was made up of the following components (where all parts areidentified with Wenger Mfg. Co. part numbers): extruder model C²TX;extruder barrel-74002-424 (head No. 1); two 74002-425 (heads Nos. 2 and3); Head No. 1 was equipped with sleeve 74002-421; Head No. 2 wasequipped with sleeve 74002-422; Head No. 3 was equipped with sleeve74002-423. Final die—74002-527 NA; 65534-029 AD; 31950-399 IN; and65422-199 BD. A rotating knife assembly was positioned adjacent theoutlet of the die for cutting the extrudate into a convenient size. Theknife assembly included the following: 19462-023 (knife blade holder)and ten knife blades (19430-007).

[0086] The preconditioner used in these runs was a Wenger Model 54 DDCpreconditioner having configuration 377 with the right and left shaftscontaining 60 beaters each. The extruded product of runs 29 and 30 wasthen dried.

[0087] The following table sets forth the operating conditions for theextruder device in the run. TABLE 12 Run #29 Run #30 Run #31 DRY RECIPEINFORMATION: Feed Screw Speed rpm 29 39 25 PRECONDITIONER INFORMATION:Preconditioner Speed rpm 250 250 250 Steam Flow to kg/hr 932 1049 1183Preconditioner Water Flow to lb/hr 500 770 470 PreconditionerPreconditioner Additive kg/hr 89 125 — 1 Rate Preconditioner Discharge °F. 188 180 202 Temperature EXTRUSION INFORMATION: Extruder Shaft Speedrpm 600 728 600 Motor Load % 50 70 62 Water Flow to Extruder lb/hr — —100 Control/Temperature ° F. W/251 W/251 W/279 2nd HeadControl/Temperature ° F. W/155 W/153 W/172 3rd Head Head/Pressure kPa4826.5 4826.5 4137 DRYER INFORMATION: Zone 1 Temperature ° C. 130 135 —Zone 2 Temperature ° C. 130 135 — Retention Time—Pass 1 min 9.2 5.7 —Retention Time—Pass 2 min 11.2 9.6 — Dryer Discharge Moisture % wb 13.288.32 — Fan Speed 1 rpm 1815 2335 — Fan Speed 2 rpm 1815 2305 — Fan Speed3 rpm 1805 2355 — Fan Speed 4 rpm 1800 2360 — FINAL PRODUCT INFORMATION:Extruder Discharge Rate kg/hr — 8040 — Extruder Discharge Density kg/m³481 450 424 Extruder Performance — Stable Stable Final ProductDescription Dog ZD Dog ZD —

[0088] Embodiment of FIGS. 7-10

[0089] FIGS. 7-10 illustrate a twin screw extruder 14 as previouslydescribed, in combination with an improved die assembly 88, the latterbeing mounted on the front face of barrel head 32. Broadly, the assembly88 includes a tubular barrel 90 presenting an internal passageway 91, anoutwardly flared output opening 92, and a pair of concentric, opposed,upwardly and downwardly extending tubular extensions 94, 96. As bestseen in FIGS. 7 and 9, the rearward end of barrel 90 is flanged to matewith the end of barrel section 32, and bolts 98 are employed to connectthe barrel in place. As depicted in FIG. 8, a conventional, apertureddie plate 100 is normally secured to the forward end of the barrel 90,across output opening 92.

[0090] The assembly 88 further includes a vertically shiftable valvestem 102 situated within the extensions 94, 96, and extending across thepassageway 91. The stem 102 includes a central through opening 104 whichis sized so that, when the stem is positioned as illustrated in FIG. 7,the opening 104 is concentric with and of the same diameter aspassageway 91. In addition, the stem has a downwardly extending tubularleg 106 which communicates with an upper opening 108, the latter alsobeing sized to mate with passageway 91 when the stem is in the positionillustrated in FIG. 9. The stem 102 is equipped with an upwardlyextending cylindrical block portion 110 above opening 104. The blockportion 110 supports a guide 112 and has a central threaded bore 114adjacent the upper end thereof. As best seen in FIGS. 7 and 9, theextensions 94, 96 have conventional O-ring seals 116, 118 adjacent theouter ends thereof, to provide a seal between the extensions and stem102.

[0091] A drive assembly 120 is provided for the stem 102 and includes apiston and cylinder unit 122 positioned above block portion 110. Theunit 122 includes a cylinder 123 equipped with apertured top and bottomwalls 123 a, 123 b, and an extensible piston rod 124, the latter passingthrough guide 112 and being threaded into block portion 110. The unit122 is supported by bolt connections to a pair of upstanding sidewalls126, 128 (see FIG. 10), the latter being secured to extension 94. Inorder to assist in determining the position of stem 102, the outer endof piston rod 124 has a pointer 130, and a rule 132 is secured to topwall 123 a. Up and down reciprocation of stem 102 is guided by means ofplate 112 slidably received between two upright plates 134, 136 whichare connected to extension 94 and plate 123 a.

[0092] In the use of assembly 88, the stem 102 is infinitely adjustablethrough the piston and cylinder unit 122. During steady-state extrusionrunning, the stem 102 may be in the FIG. 7 position, i.e., with theopening 104 concentric with passageway 91. This orientation presentsminimum restriction to flow of material passing through the extruder.However, if more back pressure is desired, the stem 102 may be raised orlowered slightly to effect partial blockage of the opening 104.Additionally, during startup operations or in the course of a changeoverbetween extruder recipes, it may be desirable to dump the material fromthe extruder barrel. This is accomplished by elevating the stem 102 tothe FIG. 9 position, where the opening 108 is in full communication withpassageway 91. In this condition, the scrap material is diverteddownwardly through tubular leg 106. Once acceptable product is beingcreated, then of course the stem 102 is lowered to the FIG. 7 positionor some intermediate position based upon desired running condition.

[0093] Embodiment of FIGS. 11-14

[0094] FIGS. 11-14 illustrate an embodiment of the invention especiallydesigned for extraction of oil from oil seeds, e.g., extraction ofsoybean oil from full-fat soy meal or soybeans. In this instance, theextruder 138 is a three-head design, as in the case of previouslydescribed extruder 14. Moreover, apart from final head 32, the extruder138 is identical with the extruder 14, and like reference numerals havebeen applied in FIG. 11. More broadly, in this aspect of the invention,use is made of one or more extraction heads similar to identical to thefinal head 32. Although not shown in the drawings, the assembly 88 ispreferably mounted adjacent the outer end of the extruder barrel.

[0095] Referring to FIGS. 11 and 12, it will be seen that the extruder138 has a modified third or final head 140 which is bolted to head 30via bolts 142. The head 140 includes an outer circular shell 144 havinga lowermost tubular fluid outlet 146; the shell 144 is supported byspaced apart head plates 148, 150. In addition, the head 140 includes aninternal, slotted extraction sleeve 152 which is made up of a series ofinterconnected, aligned bar elements 154 (see FIG. 13). The sleeve 152is of tapered configuration and is mounted within generally ovalopenings 156, 158 formed in head plates 148 and 150, respectively. Theinterior surface 160 of sleeve 152 is of horizontal, generally “FIG. 8”design, and is tapered from plate 148 to plate 150, so as to accommodatethe sections of twin screw assembly 122.

[0096] The sleeve 152 is formed of bar elements 154, each such barelement having an inner surface 162, an outer surface 164, a forwardconnection block 166, a rearward connection block 168, and a recess 170between the blocks 166, 168. The surface 169 of element 154 remote fromrecess 170 is planar throughout the length of the bar element. It willbe observed that the inner surface 162 of each bar element is shorter inlength than the corresponding outer surface 164, i.e., the radius ofcurvature of the surface 162 is smaller than that of the outer surface164. FIG. 14 illustrates a pair of side-by-side bar elements 154 a and154 b, which are interconnected by welding or other connection means atthe regions of the blocks 166 a, 166 b and 168 a, 168 b. However, owingto the recess 170 a formed in the bar element 154 a, and the adjacentplanar surface 169 b, a through passageway 172 is defined between thebar elements 154 a and 154 b.

[0097] As indicated, the entirety of sleeve 152 is made up of barelements with through passageways between adjacent bar elements. The barelements are configured so that the through passageways are tapered fromthe inner surface 160 of the sleeve 152 to the outer surface thereof. Inone embodiment, the width of the passageways adjacent the inner surfaceof the sleeve is approximately 0.003 inch (and should range from about0.001-0.065 inch). In this way, the extracted fluid may pass through thepassageways, but little or none of the solid material passing throughthe sleeve can migrate through the passageways. As best seen in FIG. 12,the bar elements at the upper and lower central regions 174 of thesleeve 152 are substantially of constant thickness, whereas those at theside arcuate sections 176 of the sleeve are themselves tapered.

[0098] The outer end of the extruder 138 includes an intermediate plate178 having a through opening 180, as well as a die mounting plate 182presenting an outwardly flared opening 184. The plates 178, 182 aresecured to plate 150 by means of bolts 186. Although not shown, it willbe appreciated that an apertured die plate may be affixed to the outersurface of plate 182 across opening 184, or more preferably the dieassembly 88.

[0099] In the use of extruder 138, a material to be defatted is passedthrough the extruder 138 where it is subjected to increasingtemperature, pressure and shear in the first two heads 28 and 30. As thematerial enters the third head 140, the action of the screw assembly 128causes oil within the oil seed material to be pressed or extrudedthrough the passageway 172 provided between adjacent bar elements 154.This oil is collected within the shell 144 and is drained via outlet 146for downstream processing (e.g., flashing and extraction). Of course,where appropriate a pump may be operatively coupled with outlet 146.After the de-oiled material passes through the sleeve 152, it movesthrough the openings 180, 184 (and if present, a die plate or theassembly 88).

[0100] A particularly preferred extraction technique using extruder 138is supercritical extraction wherein an extractant such as carbon dioxideor propane, or mixtures thereof, is injected into head 140 (or upstreamthereof into heads 28 or 30) through injectors (not shown) where theextractant is injected under supercritical temperature/pressureconditions. Such supercritical extraction results in an increase inefficiency, because the supercritical extractant is more missible withthe oil and lowers the oil viscosity, allowing it to be more easilydispelled through the sleeve 152. Further, the defatted meal is ofhigher quality because use of supercritical fluids lowers thetemperature of the meal preventing overheating thereof. This same effectinhibits oxidation of the extracted oil because of the substantialabsence of oxygen.

[0101] Where supercritical extraction is desired, it is often useful toattach a pressure regulating valve to the outlet 146 in order tomaintain pressure conditions within the head 32 (of course the “plug” ofmaterial passing through the sleeve 152 prevents venting ofsupercritical fluid rearwardly or forwardly from the sleeve). By way ofillustration only, where carbon dioxide is used as a supercriticalextractant, the pressure conditions within the sleeve 152 may bemaintained at a level of around 1500 psi, whereas within the shell 144,the pressure may be on the order of 1000 psi (i.e., there is about a 500psi pressure drop across the sleeve 152). Furthermore, it iscontemplated that a series of spaced pressure regulating valves can beattached to the outlet 146 so as to permit cascade recovery of differentproducts at different, successively lower pressures.

[0102] While the extruder 138 has particular utility for the extractionof oils, it could also be used for extraction of special tea or herbmaterials.

We claim:
 1. An extruder head comprising an elongated body having anouter shell and an inner extraction sleeve disposed within said shell,said sleeve having an inner surface defining an internal, elongatedpassageway adapted to receive at least one extrusion screw component andan outer surface, with a plurality of slots formed in the sleeve andextending from said inner surface to said outer surface, said slotsconfigured to permit an extracted fluid to pass therethrough forcollection in said shell.
 2. The extruder head of claim 1, wherein saidshell includes an extracted fluid outlet.
 3. The extruder head of claim1, at least certain of said slots being tapered and having a widthadjacent said inner surface which is less than the width thereofadjacent said outer surface.
 4. The extruder head of claim 1, saidpassageway being tapered along the length thereof.
 5. The extruder headof claim 1, said passageway being of generally FIG. 8 configuration toaccommodate side-by-side extrusion screws.
 6. The extruder head of claim1, said sleeve formed of a plurality of interconnected, elongated bars.7. An extruder comprising an elongated barrel presenting a materialinlet and a material outlet; and at least one elongated axiallyrotatable, helically flighted screw located within said barrel andoperable for moving material from said inlet to said outlet, said barrelincluding a section having an outer shell and an inner extraction sleevedisposed within said shell, said sleeve having an inner surface definingan internal, elongated passageway receiving a portion of said screw andan outer surface, with a plurality of slots formed in the sleeve andextending from said inner surface to said outer surface, said slotsconfigured to permit an extracted fluid to pass there-through forcollection in said shell, said at least one screw and said sleevecooperatively configured for extraction of fluid from said materialduring passage through said barrel section, and collection of said fluidwithin said shell
 8. The extruder of claim 7, wherein said shellincludes an extracted fluid outlet.
 9. The extruder of claim 7, at leastcertain of said slots being tapered and having a width adjacent saidinner surface which is less than the width thereof adjacent said outersurface.
 10. The extruder of claim 7, said passageway being taperedalong the length thereof.
 11. The extruder of claim 7, said passagewaybeing of generally FIG. 8 configuration to accommodate side-by-sideextrusion screws.
 12. The extruder of claim 7, said sleeve formed of aplurality of interconnected, elongated bars.
 13. The extruder of claim7, said section being located adjacent said outlet.